In recent years several African national parks have been faced with the ‘hippo problem’ — a large population of hippos accused of causing serious erosion and habitat destruction. Should they be culled? Uganda decided yes, in the Rwenzori National Park (formerly Queen Elizabeth); but the Zaire (formerly Belgian Congo) parks have always been regarded as strict nature reserves and no killing has been allowed. However, at a joint meeting of the Survival Service and the National Parks Commissions, at Kinshasa, last September, the question was raised in regard to the Virunga (formerly Albert) National Park. The commissions were asked to advise the Parks Administration on the possible relationship between the hippopotamus population and the erosion of land adjacent to the Semliki, Rutshuru and Rwindi rivers. It had been suggested that a hippopotamus population explosion in recent years was responsible for overgrazing and damage to the river banks, increasing erosion to such a degree that the whole river valley was threatened with denudation and destruction. Should the hippopotamus population be culled? Dr Paul Leyhausen was among the delegates who were able to visit the Virunga park in the course of the IUCN meetings, and in this note records his observations and conclusions on the problem and incidentally gives some idea of the complications of the situation.